Cold holdover element



Patented Apr. 24, 1951 COLD HOLDOVER ELEMENT Yves Lhermitte and Raoul Besson, Bobigny, France, assignors to Societe Anonyme dite: Glaces et Cremes Glacees Ch. Gervais, Bobigny,

France N Drawing. Application July 31, 1946, Serial No. 687,522. In France April 5, 1946 4 Claims. (Cl. 62-1) perature has been ensured by the. employment (a) Efither ice, or freezing mixture in a doublewalled receiver, with the product to be preserved placed inside the inner container.

(11) Or slabs of eutectic mixture in preservers that are made generally of copper, tin-plated to avoid corrosion.

(0) Or small slabs of carbo-ice, packed with the product to be preserved in boxes, tightly insulated, in corrugated cardboard or in insulated bags.

(d) Or finally, an eutectic mixture absorbed by a porous or jellifiable material.

The first two of these preserving methods offer I serious disadvantages because they involve material, that is expensive, has a considerable weight and bulk and that soon gets dirty. The fittings of a transport lorry, or the carriage byrail using one or the other of these methods, necessitates quite a large dead weight in the way of containers. The sale by retail of small amounts could not be carried out either by one or the other of these methods, as the expensive containers cannot be regarded as lost packages and must be got back from the purchaser.

The third method allows for the fitting of the lorry, the carriage by rail and the sale by retail with package included. However, the carboice on the one hand ofiers the handicap of rapid evaporation, that necessitates the making-up of the package at the time of the sale, on the other hand the obligation of too low and evaporation temperature that involves special safeguards for the avoidance as much as possible of having for the goods too low a temperature that may be prejudicial to the appearance, grade and flavor of l the preserved articles.

The gourth method does away with the previous disadvantages, but it shows another. The cheap porous products, such as staple fibre or similar material, wool waste, paper, cotton, cottonwool, soaked in an eutectic solution, allow oozing afterthejellification is over of the contained liquid if they are even slightly compressed and run the risk in transit of soiling the preserved article if the wrapper holding it is not perfectly Watertight. 1

The solid materials such as brick, plaster, etc. show the same drawback in a minor degree.

The jellifiable materials, that are free of the above defect, cost more and must be moulded in a rigid box that itself is expensive. I'

The preserving at a fixed temperature of goods intended to be taken hot has been ensured up till now by means of Dewar flasks or of insulated containers which show the drawbacks of brittleness, largesize, and serious dead weight.

The preserving method, that forms the object of the invention is a cure for all these diiferent drawbacks. It allows the preparation of packings at little cost and the packing obtained can be regarded as a, discard for retail sales, holds a temperature sufficiently constant and equal to what is required, depending on the kind of product to be preserved; it ofiers a negligible dead weight for the fitting of lorries and carriage by rail; it may be got ready a long time ahead and preserved in a cold or hot container in accordance with its destination; it may be used again many timesand does not show the great drawback of allowing any oozing of liquid under a gentle compression. 7

This processis essentially characterized by the fact that a eutectic mixture in the liquid state suitably chosen with reference to the temperature most suitable for the good conservation of the food product treated and capable of liberating at a constant temperature of melting (or of aqueous crystallization) the cold or heat which it contains, is absorbed according to a particular process, by a, porous material with closed cells or semi-capillaries in which it will not be absorbed in appreciable quantities by simple immersion. Consequently, the liquid cannot leave the supporting material neither spontaneously nor by moderate compression.

Among the materials capable of being utilized preferably in the form of simple plates, there may be cited as examples:

Certain imported woods, of rapid growth, such as balsa wood (West Indian corkwood) with closed or semi-closed cells, that is very light and porous.

Some artificial products with closed cells such as cellular concrete.

Some kinds of material prepared especially for the production of capillary cells, such as slabs of activated carbon.

These materials exhibit the properties of absorbing only a very small weight of liquid after an extended immersion in the eutectic solution. Thus, a slab of balsa wood measuring cm. x 1 cm. and weighing 12 grams absorbs only about 10 gr. of an eutectic solution of of potassium chloride in water.

It is easy to understand this since the air contained in the closed cells or capillaries prevents the penetration of liquid.

The absorption method employed by us consists of three phases:

1. Degassing under prolonged vacuum of the porous material with or without the help of heat. The air contained in the cells is thus drawn out.

2. Delivery of the eutectic solution into the emptied container in such a way as to cover entirely the slabs to be impregnated.

3. Admission of atmospheric pressure or compressed air above the liquid.

By this means, the liquid finds its way by diffusion into all the cells emptied beforehand of air. In 24 hours complete absorption is obtained.

Thus the small slab'of balsa wood measuring 10 cm. x 10 cm. x 1 cm., the surface adsorption of which reached only 12 gr. of eutectic solution by immersion, absorbs by the method described 140 to 150 grs. of eutectic solution.

The eutectic solution may be any of those that correspond to the temperature of conservation of the food product treated. For certain products, such as ice cream, it is preferable to employ the following solutions, it being understood that these are given only by way of example:

Solution of 200 g. of potassium chloride KCl in 800 g. of water which absorbs '72 large calories at the constant temperature of .11.2 C.

Solution of 200 g. of sodium chloride NaCl in 800 g. of water which absorbs 55 large calories at the constant temperature of 22 C.

There may also be employed for products to be conserved hot, a solution of Na2SO4.10I-I2O melted in its water of crystallization which liberates in crystallizing, 62 calories at the constant temperature of 33.

The slabs prepared in this way, if left standing for some hours or subjected to a slight compression, allow the oozing of a small amount of liquid from the surface cells. After drying and packing, the slabs are cooled below the temperature of freezing of the eutectic solution employed (or heated above the temperature of fusion of the salt forming the base of the solution). Finally, they are placed about the food product to be conserved in volume more or less great according to the degree of conservation of the product. The control of the temperature of the conservation medium is then realized by the liberation of the cold at the constant temperature of melting of the ice eutectic (or by the liberation of heat at the constant temperature of crystallization of the salt in its water of crystallization).

The slabs may act thus either as a source of cold or of heat for a lorry preferentially of the even temperaturetype, or for the makingup of a parcel intended for forwarding by rail, or for retail sale of a packet to be carried away consisting for instance of a box of light cardboard containing several eutectic slabs with the oods.

The complete packing which we may call parcel on sale to be carried away thus made up may be preserved in a cold or hot chamber 4 without any restriction as to the length of time other than that of the provisions themselves and may be taken out at any time with the preservation guaranteed. Besides, the complete package with an anticipated time of preserving of 5 hours may, if not undone, be put back into a cold or hot chamber before the end of this period and it will resume in this chamber its original condition after a certain time. It can then be taken out again with a further guaranteed preserving time of 5 hours.

The method of preserving disclosed above, provided that the eutectic mixture, has been selected properly, may be put into practice with a range varying from C. above freezing point to 30 C. below freezing point.

What we claim is:

1. A constantly dry cold-accumulating element for packing means for use in the storage of perishable goods comprising a rigid non-deformable material possessing a cellular structure including substantially closed cells interconnected by capillary ducts and substantially completely filled with a cryohydric eutectic salt solution, said cells having been preliminarily subjected to a prolonged vacuum until the air is substantially expelled therefrom, said solution being frozen whereby said element is adapted to yield up the cold stored therein upon liquefaction of said solution at the constant temperature of its eutectic point, and whereby the liquid resulting from said liquefaction remains permanently entrapped in said closed cells, and whereby the dry element can be refrozen for reuse.

2. A constantly dry cold-accumulating element for packing means for use in the storage of perishable goods comprising a board of balsa wood whose substantially closed cells intercom nected by capillary ducts are substantially completely filled with a cryohydric eutectic salt solu-- tion, said cells having been preliminarily sub jected to a prolonged vacuum until the air is substantially expelled therefrom, said solution being frozen whereby said element is adapted to yield up the cold stored therein upon liquefaction of said solution at the constant temperature of its eutectic point, and whereby the liquid resulting from said liquefaction remains permanently entrapped in said closed cells, and whereby the dry element can be refrozen for reuse.

3. A constantly dry cold-accumulating element for packing means for use in the storage of perishable goods comprising a board of cellular concrete possessing a cellular structure including substantially closed cells interconnected by capillary ducts and substantially completely filled with a cryohydric eutectic salt solution, said cells having been preliminarily subjected to a prolonged vacuum until the air is substantially expelled therefrom, said solution being frozen whereby said element is adapted to yield up the cold stored therein upon liquefaction of said solution at the constant temperature of its eutectic point, and whereby the liquid resulting from said liquefaction remains permanently entrapped in said closed. cells, and whereby the dry element can be refrozen for reuse. A

4. A constantly dry cold-accumulatingelement for packing means for use in the storage of perishable goods comprising a plate of activated carbon possessing a cellular structure including substantially closed cells interconnected by capillary ducts and substantially completely filled wit e cryohydric eu ectic salt solution, s d cells ms LHERMIT'IE. RAOUL BESSON.

6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 64,703 Pustkuchen May 14, 1867 2,011,426 Taylor et a1. Aug. 13, 1935 2,039,736 Munters et a1. May 5, 1936 2,167,215 Leary July25, 1939 2,208,855 Riley July 23, 1940 2,210,946 Moore Aug. 13, 1940 2,418,745 Bartlett Apr. 8, 1947 

